<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>4-1</title>
  <script src='vue/vue.js'></script>
</head>

<body>
  <div id="root">
    <counter ref='one' @change='handleChange'></counter> 
    <!-- change是$emit触发的事件 -->
    <counter ref='two' @change='handleChange'></counter>
    <div>{{totle}}</div>
  </div>
  <script>
    Vue.component('counter', {
      template: "<div @click='handleClick'>{{number}}</div>",
      data: function () {
        return {
          number: 0
        }
      },
      methods: {
        handleClick: function () {
          this.number++
          this.$emit("change")
        }
      }
    })
    var vm = new Vue({
      el: "#root",
      data: {
        totle: 0
      },
      methods: {
        handleChange: function () {
          console.log("ok");
          this.totle = this.$refs.one.number + this.$refs.two.number
        }
      }
    })
  </script>
</body>

</html>